BAUSCH 

Use  and  Care  of  the 
Microscope 


QH 

205 

B34 


£ 
. 


\HSE 


AND   CARE 


MICROSCOPE 


EDWARD  BAUSCH 


EXTRACTS  FROM 


MANIPULATION  OF  THE  MICROSCOPE 


PUBLISHED   BY 

PUBLICATION  DEPARTMENT 

BAUSCH  &  LOMB  OPTICAL  COMPANY, 

ROCHESTER,  N.  Y. 


Copyright 

4  LOME  OPTICAL  COMPANY, 
1902. 


PKBSS  OF    I  UK 

KAUSCH   A   LOMB  OPTICAL  CO., 
ROCHESTER.  N.  Y. 


USE  AND  CARE  OF  THE  MICROSCOPE. 

Extracts  from  "  Manipulation  of  the  Microscope." 

How  to  Set  Up  the  Instrument.  Draw  the 
instrument  from  the  case  by  grasping  the  base  and 
pillar ;  free  from  dust  with  a  large  camel's  hair  brush, 
i  inch  or  i  1-2  inch,  or  by  wiping  carefully  with  chamois 
skin,  or  old  linen.  Place  the  instrument  on  the  work- 
table,  which  should  be  of  such  height  that  observations 
can  be  made  with  the  utmost  possible  comfort  without 
straining  the  neck,  or  compressing  the  chest.  Bear  in 
mind  always  to  sit  as  upright  as  possible. 

If  the  instrument  is  used  in  the  upright  position, 
place  the  base  close  to  the  edge  of  the  table ;  if 
inclined,  it  may  set  farther  in.  Rest  the  arms,  as 
much  as  the  height  of  the  instrument  will  permit,  upon 
the  table. 

Bring  the  tube  to  the  standard  length  for  which  the 
objectives  are  corrected.  To  do  this  grasp  the  milled 
edge  of  the  draw-tube  and  give  it  a  spiral  motion  while 
holding  the  main  tube  with  the  other  hand.  There  is 
one  objection,  however,  that  in  any  but  cloth-lined 


sheaths  the  polished  tube  will  soon  be  scratched, 
especially  if  not  kept  very  clean.  In  stands  without 
the  graduated  tube,  a  mark  or  ring  is  or  should  be 


Correct  position  at  the  microscope. 


provided  on  it,  which  should  be  co-incident  with  the 
upper  end  of  the  main  tube.     Where  graduated   tube 


is  provided,  bring  the  proper  figure,  either  216  or  160, 
in  line  with  the  upper  end  of  the  main  tube  in 
accordance  with  the  tube  length  for  which  the  objec- 
tives are  corrected. 

Attach  low  power  eyepiece. 
Attach  low  power  objective. 
Place  object  on  stage. 
Illuminate  object. 
Focus  on  object. 

To  Attach  Eyepiece.  The  exterior  surfaces  of 
the  eye-lens  and  field-lens,  being  exposed,  are  apt  to 
become  dusty,  and  should  always  be  carefully  cleaned 
before  using.  If  there  are  two  or  more  eyepieces,  always 
use  the  lowest  power  first.  Eyepieces  should  be  so 
loosely  fitted  that  they  will  drop  into  the  tube  as  far  as 
the  collar  by  their  own  weight.  They  do  this  slowly 
when  the  objective  is  attached,  as  an  air-tight  compart- 
ment is  formed  and  the  air  to  the  extent  of  the  dimen- 
sions of  the  eyepiece  must  first  be  expelled  from  the 
tube.  This  displacement  may,  however,  be  hastened  by 
gently  pushing  the  eyepiece  downward,  but  not  to  such 
an  extent  as  to  push  in  the  draw-tube,  or  force  down 
the  coarse  adjustment.  In  fact  care  must  be  used  in 
applying  the  eyepiece,  or  sliding  the  draw-tube,  as  the 
focus  may  be  disturbed,  or  the  objective  forced  against 
the  object  and  thus  destroy  it. 


To  Attach  Objective.  Using  a  low-power  objec- 
tive, remove  from  its  box  and  see  that  its  front  lens  is 
clean ;  elevate  the  tube  of  the  stand  by  means  of  the 
coarse  adjustment  so  that  the  nose-piece  shall  be  at 
least  two  inches  from  the  stage. 


Proper  manner  of  holding  objective  when  attaching  it  to  tube. 

Grasp  the  upper  knurled  edge  of  the  objective 
between  thumb  and  forefinger  of  the  left  hand ;  bring 
the  screw  in  contact  with  the  screw  of  the  nose-piece, 
and,  keeping  the  objective  in  line  with  the  tube  and 
gently  pressing  upward,  revolve  the  objective  with  the 
thumb  and  forefinger  of  the  right  hand  by  the  lower 
milled  edge  until  shoulder  sets  against  shoulder. 


To  properly  attach  an  objective  is  not  always 
simple,  and  cannot  be  done  too  carefully.  One  danger 
lies  in  the  fact  that  the  objective  may  be  dropped  onto 
the  object,  and  thus  injure  or  destroy  one  or  the  other 
or  both,  and  another  that  the  threads  may  be  started 
wrong  by  holding  the  objective  sideways,  and  the 
threads  thus  injured. 

To  Attach  Objectives  and  Double  Nose- 
Piece.  Screw  each  objective  into  proper  place  in  the 
double  nose-piece,  with  the  2-3  opposite  the  opening 
through  which  the  light  passes. 


Propei   method  of  attaching  nose-piece  to  microscope. 

Hold  the   nose-piece   in    the  right  hand,    objectives 
down.     Bring  the  revolving  screw  in  contact  with  the 


screw  in  the  tube,  square  with  tube ;  with  thumb  and 
forefinger  of  left  hand,  turn  milled  edge  of  the  revolving 
screw  until  it  engages,  swing  nose-piece  toward  the  front, 
and,  holding  it  in  this  position,  screiv  the  ring  home. 

The  same  procedure  as  above  holds  good  for  attach- 
ing objectives  to  the  triple  and  quadruple  nose-pieces. 

Finding  an  Object.  The  slide  upon  which  the 
object  is  mounted  is  placed  upon  the  front  of  the  stage 
and  slipped  under  the  spring  clips  to  a  point  where  the 
object  comes  as  nearly  as  possible  in  the  center  of  the 
opening  of  the  stage. 

With  low  power  objectives,  which  are  used  on  coarse 
and  large  objects,  it  will  be  found,  after  properly  focus- 
ing, that  a  portion  of  the  object  will  show  itself  in  the 
field,  and  upon  moving  the  slide  it  can  easily  be 
brought  to  the  center.  In  this  connection  it  must  be 
remembered  that  the  image  in  the  eyepiece  is  in  a 
reversed  position  from  that  of  the  object,  and  that  a 
movement  of  the  object  to  the  left  is  an  apparent 
movement  to  the  right  in  the  field.  In  case  of  a  small 
object  which  is  not  found  after  the  objective  is  known 
to  be  in  focus,  as  may  be  told  if  the  mounting  medium 
or  small  particles  of  dust  on  the  cover  glass  are 
visible,  move  the  slide  about -on  the  stage  by  grasping 
one  end  with  the  thumb  and  forefinger,  when  the 
object  can  usually  be  recognized  by  its  shadowy  out- 
lines as  it  flits  across  the  field.  The  difficulty  of 


finding  an  object  or  a  particular  spot  in  it  becomes 
more  difficult  with  the  increase  in  power,  and  even  in 
experienced  hands  sometimes  becomes  quite  vexatious. 
Recourse  may  be  had  to  two  methods  : 

By  using  a  low  power  eyepiece. 

By  using  a  low  power  objective  as  a  finder. 

A  large  field  is  thus  obtained  in  which  the  object 
may  be  more  easily  found,  and  after  moving  to  the 
center  of  the  field,  the  low  power  objective  is  removed 
and  the  high  power  attached  ;  or  in  case  the  revolving 
nose-piece  is  used,  use  the  low  power  objective  as  a 
finder,  then  swing  the  high  power  objective  into 
position,  care  being  taken  not  to  touch  the  slide,  and 
focus  in  the  manner  to  be  described.  The  object  may 
not  be  in  the  field,  due  to  a  slight  variation  in  the 
centers  of  the  objectives,  but  it  will  certainly  be  very 
close  and  ought  to  be  easily  found. 

To  Illuminate  the  Object.  This  is  an  extremely 
important  feature,  and  should  always  be  carefully  done, 
as  one  may  easily  fail  to  obtain  the  best  results,  may 
be  led  to  wrong  conclusions,  or  may  injure  the  eyes. 
The  mirrors  of  the  microscope  are  usually  plane  and 
concave,  and  are  provided^with  universal  joint  so  as  to 
be  able  to  reflect  the  light  from  any  source  in  front  or 
at  the  side  of  the  microscope. 

The  plane  mirror  reflects  the  light  in  the  initial 
intensity  of  its  source,  and  is  used  with  low  power 


objectives.  The  concave  mirror  concentrates  the  rays 
on  the  object,  thereby  giving  intensified  illumination, 
and  is  used  with  medium  and  high  power  objectives, 
except  when  substage  condenser  is  used,  when  the 
plane  mirror  only  is  employed. 

The  sources  of  light  are  either  daylight  or  artificial 
light ;  if  the  former  the  light  of  a  northern  sky  is  pre- 


Illuminating  object  with  plane  mirror.     Illuminating  object  with  concave  mirror. 

ferred,  and  if  the  latter  a  flat-wick  oil  lamp  or  Welsbach 
gas  burner.  An  ordinary  gas  flame  should  not  be  used 
on  account  of  the  difficulty  of  obtaining  equal  illumina- 
tion and  the  constant  flickering  which  is  very  injurious. 
When  using  a  flat-wick  lamp  the  narrow  edge  of  the 
flame  should  be  used,  as  this  is  more  intense  than  the 
broad  side. 

When  using  daylight  place  the  microscope,  as  nearly 
as  possible,  directly  before  a  window,  and  when  a  lamp 

8 


is  employed,  have  it  on  the  table  either  in  front  or  at 
the  right  side  of  the  microscope  and  within  easy  reach. 
Light  is  either  transmitted  or  reflected.  When  the 
former,  it  is  used  to  illuminate  transparent  objects  and 
passes  through  the  objects  from  below  the  stage  into 
the  objective.  With  opaque  objects  this  is  impossible 
and  reflected  light  is  required,  when  it  is  directed  onto 
the  object  from  above  and  illuminates  its  upper  surface. 
In  the  following  instructions  it  is  assumed  that  trans- 
mitted light  is  used  unless  otherwise  stated. 

The  concave  mirror  converges  the  light  and  its 
focus  is  of  such  length  that  with  parallel  rays  (daylight) 
the  light  will  fall  on  the  object.  With  diverging  rays 
(lamplight)  the  focus  will  be  longer,  and  while  ordinarily 
the  mirror  may  remain  in  its  position,  it  is  advisable 
in  critical  work  to  properly  focus  the  mirror  by 
increasing  its  distance  from  the  object. 

Before  lighting  an  object  make  certain  that  the 
mirror  bar  is  in  exactly  central  position,  and  set  the 
mirror  at  such  an  angle  to  the  light  that  it  will  be 
reflected  upon  the  object,  which  can  be  done  more 
quickly  at  the  outset  by  observing  the  object  or  the 
opening  of  the  stage,  keeping  the  head  at  one  side  of 
the  tube.  Now  remove  the  eyepiece,  and  observe  the 
light  through  the  objective.  It  should  be  central  and 
of  equal  intensity,  which  with  daylight  is  sometimes 
difficult  to  obtain  as  the  sash  of  the  window  may  be 
reflected  and  show  itself  in  the  field  as  dark  bands,  or 


in  the  case  of  lamplight  the  blue  portion  of  the  flame 
may  appear  as  a  dark  spot.  These  are  only  preliminary 
directions  but  will  suffice  for  a  beginning.  There  will 
be  little  difficulty  in  obtaining  proper  illumination  at 
the  outset  if  one  will  observe  the  following : 

Remove  the  eyepiece  and,  looking  through  the  back 
of  the  objective,  have 

Central  illumination. 

Even  illumination  over  the  entire  field. 

Mellow  illumination. 

Defects  in  illumination  which  may  not  be  apparent 
will  show  when  the  eyepiece  is  replaced,  and  are 
indicated, 

When  dark  points  or  shadows  appear  in  the  field. 

When  the  outlines  of  an  object  are  bright  on  one 
side  and  dark  on  the  other. 

When  the  object  appears  to  lie  in  a  glare  of  light. 

In  the  first  two  cases  the  correction  can  be  made 
by  suitably  adjusting  the  position  of  the  mirror,  in  the 
last  by  reducing  the  amount  of  light  by  the  use  of  a 
diaphragm. 

It  is  now  generally  conceded  that  observations  with 
the  microscope  may  be  made  to  any  extent  without 
any  detrimental  results  to  the  eyes,  provided,  however, 
that  the  conditions  of  light  are  just  right.  It  is  a  good 
rule  to  follow,  to  use  as  small  an  amount  of  illumination 


as  will  comfortably  show  the  structure  which  is  being 
studied,  and  it  may  also  be  safely  accepted  that,  if  the 
eye  tires  or  feels  uncomfortable,  the  light  should  be 
moderated. 

Illumination  is  either 

Central  or  axial,  when  the  center  of  the  mirror  is 
in  the  optical  axis,  or 

Oblique,  when  the  mirror  is  swung  to  one  side, 
which  in  objectives  of  wide  aperture  will  disclose  struc- 
ture that  cannot  be  seen  with  central  illumination. 

To  focus  an  objective  is  to  adjust  its  relation  to 
the  object  so  that  a  clear  image  is  obtained.  Focusing 
should  involve  no  danger  to  the  front  lens  of  the  objec- 
tive, or  to  the  cover  glass  by  their  coming  in  violent 
contact.  With  the  low  power  objectives,  in  which  the 
working  distance  is  great,  there  should  be  little  danger; 
with  the  higher  power  objectives,  in  which  the  working 
distance  is  so  small  that  the  front  of  the  objective  is 
very  close  to  the  cover  glass,  there  is  considerable. 

To  focus  low  power  objectives  : 

Attach  objective  to  the  nosepiece.  Lower  the  head 
to  the  level  of  the  stage,  watching  the  front  of  the  objec- 
tive ;  lower  the  tube  by  the  coarse  adjustment  until  the 
front  of  the  objective  is  within  one  quarter  inch  of  the 
object ;  look  through  the  eyepiece  and  slowly  elevate  by 
the  coarse  adjustment  until  the  image  is  distinct.  Use 
fine  adjustment. 


The  upward  movement  should  be  slow  so  that,  if 
the  object  be  faint,  it  is  not  missed  and  the  adjustment 
not  run  beyond  its  focal  distance ;  or  it  is  possible  that, 
in  the  case  of  a  very  minute  object,  it  may  be  out  of 
the  center,  and  thus  out  of  the  field  of  vision,  in  which 
case  the  surface  of  the  cover  glass,  or  the  minute 
particles  of  dust  upon  it  should  be  distinguishable. 

The  object  will  first  appear  with  faint  outlines  and 
indistinct ;  then  gradually  more  distinct,  and  finally 
sharply  defined,  and  if  adjustment  goes  beyond  this 
point,  it  will  gradually  become  more  dim,  in  which  case 
return  to  the  point  of  greatest  distinctness. 

To  focus  high  power  objectives  : 

Attach  objective  to  nose-piece.  Lower  the  head  to 
the  level  of  the  stage  and  look  between  objective  and 
cover-glass  toward  a  window  or  aflame.  Slowly  lower 
the  objective  with  the  coarse  adjustment  until  the  front 
of  the  objective  is  nearly  in  contact  with  the  cover  glass  ; 
look  into  the  eyepiece,  slowly  elevate  the  tube  of  the 
coarse  adjustment  until  the  image  appears.  Use  fine 
adjustment. 

It  is  also  advisable  while  watching  for  the  image 
to  appear  to  move  the  object  slowly  in  different  direc- 
tions, as  the  flitting  of  shadows  or  colors  across  the 
field  will  give  indications  that  the  objective  is  nearing 
the  focal  point. 


Always  focus  upward.  In  case  a  low  power  is 
exchanged  for  a  higher  power  objective,  or  when  the 
low  power  has  been  used  as  a  searcher,  i.  e.,  to  find  a 
certain  object  in  a  collection,  or  a  certain  locality  in  a 
specimen,  the  tube  should  first  be  elevated,  as  working 
distance  in  the  high  power  is  too  short  to  admit  of 
screwing  it  into  the  nose-piece,  then  detach  the  low 
power,  attach  the  high  power  and  proceed  to  focus  in 
the  order  given. 

Objectives  which  make  up  the  regular  outfits  are  so 
adjusted  as  to  be  par  focal,  i.  e.,  are  so  fitted  to  the  nose- 
piece  that  as  either  one  is  swung  into  position,  it  is  so 
nearly  focused  as  to  require  the  use  of  the  fine  adjust- 
ment only.  Very  low  power  objectives  vary  so  much  in 
their  focal  lengths  from  those  powers  which  make  up 
the  outfit  that  it  is  generally  impossible  to  make  them 
par  focal.  The  2-3  and  1-6  or  1-8  on  the  double  nose- 
piece,  and  2-3,  1-6  or  1-8  and  the  1-12  oil  immersion  on 
the  triple  nose-piece  are  so  made.  But  in  a  combina- 
tion of  a  lower  power  with  2-3  and  1-6  on  the  triple 
nose-piece,  or  a  lower  power  with  the  2-3,  1-6  and  1-12 
on  a  quadruple  nose-piece,  it  is  impossible  to  get  the 
lower  power  par  focal  with  the  others. 

As  the  adjustment  of  the  objectives  to  make  them 
par  focal  is  quite  delicate,  each  arm  of  the  nose-piece 
is  marked  to  correspond  with  the  power  of  the  objec- 
tive which  is  to  go  into  it.  Furthermore  it  is  highly 
important  to  preserve  proper  tube  length.  In  the  short 

13 


tubes  the  objectives  are  adjusted  for  exactly  i6o.omm. 
distance  and  if  no  revolving  nose-piece  is  used,  should 
be  set  for  this  length.  With  the  revolving  nose-piece 
the  tube  should  be  contracted  so  that  the  ring  of  the 
draw-tube  rests  upon  the  shoulder  of  the  main  tube. 

To  focus  with  double  nose-piece  : 

Contract  tube,  focus  with  2-3  objective,  then  swing 
nose-piece  until  1-6  nears  the  cover  glass,  lower  the  head 
to  the  level  of  the  stage  and  endeavor  to  slowly  swing 
objective  into  place.  Should  the  front  of  the  objective 
threaten  to  come  in  contact  with  the  cover  glass,  the  tube 
must  be  elevated  and  the  objective  focused. 

The  method  of  procedure  with  triple  and  quadruple 
nose-pieces  is  very  much  the  same  as  with  the  double, 
and  the  same  rules  will  apply. 

Oil  Immersion  Objectives.  Immersion  contact 
between  the  objective  and  cover  glass  is  made  \\ith 
cedar  oil.  This  is  specially  prepared  so  as  to  have  the 
same  refractive  index  as  glass  and  great  care  should  be 
used  to  keep  it  free  from  dust.  Apply  the  smallest 
quantity  to  the  front  lens,  by  allowing  the  superfluous 
amount  to  run  from  the  rod  or  brush,  before  objective 
is  attached  to  nose-piece.  If  air  bubbles  are  contained 
in  the  oil,  remove  it  and  apply  a  fresh  quantity.  This 
is  exceedingly  important,  as  the  presence  of  dust  or 
air  bubbles  in  oil  may  destroy  the  definition  of  the  best 
objective. 


Attach  the  objective  and  loiver  it  until  the  fluid 
comes  in  contact  with  the  cover  ;  observe  this  by  lowering 
the  head  to  the  level  of  the  stage.  Focus  as  with  dry 
objectives. 

Special  care  must  be  observed  if  a  low  power 
objective  is  used  after  an  oil  immersion.  The  oil  must 
invariably  be  removed  from  the  top  of  the  cover  glass 
by  wiping  first  with  a  moist  cloth,  and  then  cleaning 
with  a  dry  cloth.  The  front  of  the  objective  should 
always  be  cleaned  in  the  same  manner  immediately 
after  it  has  been  used. 

To  Focus  with  Fine  Adjustment.  After  the 
focus  has  been  found  with  the  coarse  adjustment,  the 
fine  adjustment  should  be  brought  into  action,  in  order 
to  obtain  a  more  sensitive  and  reliable  adjustment  for 
focusing  through  the  different  planes  or  depths  of  the 
object.  Its  range  of  movement  is  necessarily  short 
and  at  one  end  the  screw  comes  to  a  stop,  and  at  the 
other  goes  beyond  the  limit  of  movement  and  becomes 
inoperative.  It  should  always  be  kept  as  near  as 
possible  at  the  medium  point  of  its  range.  Grasp  the 
milled  head  of  the  fine  adjustment  with  the  thumb  and 
forefinger  of  one  hand  (right)  and,  turning  the  screw  in 
either  direction,  focus  in  different  planes  of  the  object, 
while  the  other  hand  (left)  moves  the  object. 


Use  of  Substage  Diaphragm.  The  purpose 
of  the  diaphragm  is  to  modify  the  amount  of  light,  and 
by  its  aid  obtain  results  in  definition  of  the  object 
which  without  it  are  impossible.  Much  will  depend 
upon  the  density  of  the  object,  the  intensity  of  illumina- 
tion and  the  power  of  the  objective. 

Use  an  opening  in  Hie  diaphragm  of  about  the  same 
size  as  the  front  lens  of  the  objective. 

As  a  rule  this  will  be  found  to  give  a  superabundance 
of  light,  especially  in  low  power  objectives,  and  by 
reducing  the  aperture  it  will  be  found  that  there  will 
be  an  increased  differentiation  in  the  object.  The 
diaphragm  should  be  reduced  to  a  point  where  the 
amount  of  illumination  will  be  perfectly  comfortable 
to  the  eye. 

Do  not  use  so  large  an  opening  that  there  will  be 
an  uncomfortable  glare,  nor  so  small  that  undue  exertion 
is  required  to  see  structure. 

When  oblique  light  is  used,  there  should  be  no 
obstruction  to  the  course  of  light,  and  with  the  iris  and 
revolving  diaphragms  full  opening  should  be  employed. 

"Which  Eye  to  Use.  The  right  eye  is  generally 
used  for  observations,  but,  while  the  manipulator  may 
from  habit  be  inclined  to  use  this,  it  may  be  possible 
that  in  some  cases  the  left  can  be  used  to  best  advant- 
age and  with  less  fatigue. 

16 


Make  it  a  habit  at  the  outset  to  keep  both  eyes  open. 

There  is  a  point  over  the  lens  called  the  eye-point 
at  which  the  rays  cross  within  the  smallest  compass, 
and  this  is  the  proper  position  for  the  eye. 

When  above  or  below  this  point  the  size  of  field  will 
be  reduced  or  shadows  or  colors  will  appear  in  it.  In 
low  power  eyepieces  the  eye-point  is  some  distance  from 
the  lens,  in  high  power  quite  close  to  it, — in  fact,  in 
some,  so  close  that  the  eyelashes  rest  upon  the  lens  and 
sometimes  appear  in  the  field  as  dark  bars. 

Cover  Glass  and  Spherical  Correction.     The 

cover  glass  has  a  pronounced  influence  on  the  spherical 
correction  of  objectives.  A  variation  in  thickness  from 
that  used  by  the  makers  of  objectives,  while  not 
appreciable  in  low  powers,  such  as  2-3,  may  be  very 
detrimental  to  satisfactory  definition  with  a  i -6  or  a  1-8. 
Unfortunately,  this  effect  is  not  generally  known,  or  if 
so,  not  sufficiently  appreciated.  A  variation  of  0.05 
mm.  either  thicker  or  thinner  than  the  standard  thick- 
ness'is  sufficient  tg  totally  obliterate  the  fine  structure 
in  an  object,  leaving  the  coarse  fines  only  apparent,  and 
a  slighter  variation  affects  the  image  proportionately. 
There  is  no  one  thickness  adopted  by  the  different 
makers  and  some  even  allow  themselves  considerable 
latitude  in  adjusting  their  objectives,  so  that  there  is  a 
noticeably  varying  result  with  different  objectives  on 
the  same  specimen. 


Then,  too,  one  great  difficulty  lies  in  the  fact  that 
it  is  commercially  impossible  to  produce  covers  of  one 
thickness.  They  are  made  in  three  numbers  of  the 
following  thicknesses : 

No.  i.  1-150  to  1-200  inch  or  0.16  to  0.13  mm. 
No.  2.  i-ioo  to  1-150  inch  or  0.25  to  o.  16  mm. 
No.  3.  1-50  to  i-ioo  inch  or  0.50  to  0.25  mm. 

The  No.  2  cover  glasses  are  in  most  general  use, 
o.i  8  mm.  thickness  being  best  suited  to  objectives  as 
now  corrected.  A  good  plan  is  to  procure  a  cover 
glass  gauge  and  measure  the  covers. 

Set  aside  those  from  0.17  to  o.ig  mm.  thick  for  use 
on  specimens  with  which  1-6  or  1-8  inch  objectives  will  be 
used.  Those  thicker  may  be  laid  aside  for  use  with  2-3 
and  lower  flowers ,  and  the  thinner  ones  for  oil  immersion 
objective. 

Under  these  conditions  it  is  important  to  suggest 
methods  by  which  the  utmost  efficiency  of  an  objective 
may  be  obtained. 

To  judge  spherical  correction  by  use  of  histo logical 
or  biological  objects  and  on  Bacteria  and  Micrococc  i 
with  oil  immersion  objectives,  without  a  previous  know- 
ledge acquired  from  objects  which  are  more  suited, 
is  extremely  difficult,  but  a  study  in  this  direction  will 
be  found  exceedingly  valuable  in  utilizing  the  full 
capacity  of  the  objectives. 

18 


To  judge  spherical  correction  with  a  1-6  or  1-8, 
the  diatom  Pleurosigma  angulatum  is  best  suited  to  a 
preliminary  study.  Select  a  diatom  which  is  flat  and 
locate  in  the  center  of  the  field.  Focus  carefully  so 
that  the  margin  of  the  object  will  be  sharply  defined 
and  observe  the  markings.  If  they  should  show  in  the 
same  plane  without  any  further  focusing,  the  spherical 
correction  may  be  accepted  as  being  correct. 

If  the  lines  appear  to  lie  in  a  higher  plane,  and  it 
is  necessary  to  focus  upward,  so  that  the  margin  of  the 
diatom  is  out  of  focus,  it  indicates  spherical  over- 
correction  and  the  remedy  is  found  in  the  contraction 
of  the  tube  length. 

This  should   be   done   progressively    in    spaces   01^ 
about  one-half  inch,   and  after  each  change  carefully 
focus  again  until  proper  correction  is  obtained. 

When  the  lines  appear  to  lie  below  the  plane  of  the 
object,  it  indicates  spherical  under-correction,  and  can  be 
corrected  by  increasing  the  tube  length. 

If  there  are  two  or  more  eyepieces,  results  can  be 
obtained  quicker  with  the  higher  powers.  If  the  mark- 
ings cannot  be  seen  it  may  be  due  to  abnormally  thick 
or  thin  covers,  a  not  uncommon  occurrence,  thus 
destroying  the  resolving  power.  This  may  be  judged 
by  using  slightly  oblique  illumination.  If  too  much  is 
used  the  nice  differences  will  be  lost.  If  from  a  pre- 
conceived idea  of  what  any  other  object  should  show 


it  is  hazy  where  one  expects  it  to  be  distinct,  or  if  it 
fails  to  show  detail  which  is  known  to  exist,  and  being 
certain  that  the  objective  and  eyepiece  are  properly 
cleaned,  it  may  generally  be  ascribed  to  lack  of  proper 
correction.  By  focusing  either  above  or  below  the 
proper  focal  plane,  there  will  be  an  enlargement  of  the 
outlines  of  the  object  or  a  coma,  which  gradually 
enlarges  as  the  objective  recedes  from  the  proper 
focal  point. 

If  the  expansion  or  coma  is  greatest  when  the  objec- 
tive is  elevated,  there  is  spherical  over-correction,  and 
the  tube  length  should  be  decreased. 

Should  the  expansion  be  greatest  when  the  objective 
is  lowered,  there  is  spherical  under-correction  and  the 
tube  length  should  be  increased. 


ILLUMINATION    WITH    SUBSTAGE 
CONDENSER. 

Purpose  of  the  Condenser.  The  purpose  of 
the  condenser  is  to  give  an  amply  illuminated  field 
when  the  illumination  is  otherwise  insufficient,  and  to 
illuminate  the  object  with  a  cone  of  light  having  an 
angular  aperture  equal  to  that  of  the  objective,  as  well 
as  to  provide  means  for  controlling  the  amount  and 
character  of  the  illumination  to  suit  the  various  condi- 
tions of  work. 


Abbe  Condenser  1.20  N.  A.  Abbe  Condenser  1.42  N.  A. 

The  Abbe  condenser  of  1.20  N.  A.  is  in  most 
common  use  and  the  most  simple  form  of  mounting  is 
one  which  has  attached  to  its  lower  side  an  iris 
diaphragm  for  regulating  the  amount  and  angle  of  light 
and  a  vertical  screw  motion. 

The  most  complete  form  has  adjustments  for 
obtaining  every  modification  of  illumination,  with  rack 
and  pinion  for  vertical  and  lateral  adjustment. 


21 


The  condenser  should  not  be  used  on  very  low 
power  objectives  as  it  is  distinctly  harmful  and  the 
mirror  alone  provides  ample  illumination. 

Use  only  plane  mirror  with  the  condenser. 

A  condenser  is  so  constructed  that  parallel  rays  of 
light  are  brought  to  a  focus  above  the  upper  surface  of 
its  uppermost  lens  and  in  the  plane  of  the  object, 
If  the  concave  mirror  is  used  the  convergence  of  light 
is  more  rapid  and  the  apex  of  the  cone  of  light  is  \vithin 
the  condenser  and  its  effectiveness  depreciated. 


Illuminating  object  with  condenser 
and  plane  mirror.  The  right  way. 


Illuminating  object  with  condenser  and 
concave  mirror.    The  wrong  way. 


Centering  the  Condenser  is  the  act  of  bringing  its 
optical  axis  coincident  with  the  optical  axis  of  objective. 

To  verify  correct  centering  two  easy  methods  may 
be  followed : 

/.  Use  a  2-inch  objective  and  focus  through  the 
condenser  onto  the  diaphragm,  which  is  reditced  to  its 
smallest  opening. 


//.  Use  a  2-3  or  i  inch  objective ;  focus  upon  upper 
surface  of  condenser  or  upon  an  object  which  should 
then  be  removed ;  elevate  objective  with  coarse  adjust- 
ment until  a  dimly  defined  dark  spot  appears  in 
the  field  and  with  proper 
focusing  is  about  i-j  of  the 
diameter  of  the  field. 

Centering  of  the  con- 
denser does  not  imply  that 
the  cone  of  illumination  is 
also  centered  and  it  is 
fully  as  important  to  secure 
the  correct  conditions  in 


one  as  it  is  in  the  other. 


Complete  Substage.     Front  View. 


Centering  the  Illumination.  The  mirror  may 
be  so  adjusted  that  the  light  will  be  directed  toward 
the  periphery  of  the  condenser  and  when  lamplight  is 
used  the  light  may  be  so  placed  as  to  give  all  grada- 
tions of  oblique  illumination  from  the  central  to  the 
limit  of  aperture,  although  the  condenser  may  be 
centered. 

•    With  daylight  have  evenly  illuminated  field. 

With  lamplight  attach  2-3  inch  objective ;  open  dia- 
phragm to  full  extent  and  focus  upon  the  minute  image 
of  flame  ;  adjust  mirror  so  that  the  image  will  be  in  the 
center  of  the  field. 


2  3 


To  Focus  Condenser.  In  all  the  various  forms 
of  mountings  the  condenser  is  so  mounted  that  at  the 
uppermost  limit  of  adjustment  its  upper  surface  is  just 
below  the  surface  of  the  stage  so  that  it  cannot  come 
in  contact  with  the  slide. 

With  all  objectives  having  a  numerical  aperture  less 
than  i.o  the  condenser  may  be  used  dry,  i.  e.,  without  oil. 


Complete  Substage.     Front  view,  with  condenser  and  lower  iris 
diaphragm  swung  out  of  optical  axis. 

In  the  use  of  the  condenser  with  oil  immersion 
objectives  the  custom  prevails  of  using  the  condenser 
dry.  It  is  well  to  point  out,  however,  that  both  the 
condenser  and  the  objective  lose  in  their  efficiency 
when  the  former  is  used  dry,  and  for  critical  work  the 
condenser  should  be  in  immersion  contact  with  the  slide. 

To  make  immersion  contact  between  condenser  and 
slide  place  a  drop  of  oil  on  the  top  of  condenser,  drop  the 
slide  upon  the  stage,  first  throwing  the  clips  to  one  side. 


With  immersion  objectives  the  proper  focusing  of 
the  condenser  becomes  a  matter  of  nice  distinction  to 
obtain  best  results  and  can  only  be  reliably  accomplished 
by  considerable  practice  and  experience.  To  obtain 
best  position  : 

Use  a  2-j  objective ;  focus  upon  the  object ;  adjust 
condenser  until  image  of  window-sash  or  flame  is  in  the 
same  plane  with  the  object. 


Complete  Substage.    Top  view,  with  condenser  and  lower  iris 
diaphragm  swung  out  of  optical  axis. 

Relation  of  Aperture  of  Condenser  to 
Objective.  In  the  study  of  Bacteria  and  other  micro- 
organisms, the  objectives  used  being  of  wide  aperture, 
it  is  sought  to  have  them  stand  out  boldly  in  a  bright 
field.  This  is  accomplished  by  bringing  the  diaphragm 
to  its  full  aperture.  On  all  other  objects,  however,  too 
much  illumination  decidedly  injures  definition  by 
obliterating  detail. 


Little  experience  is  required  to  judge  when  the  con- 
denser has  its  proper  opening.  When  correct,  the  image 
will  stand  out  sharply  defined  without  any  appearance 
of  fogginess  and  as  the  diaphragm  aperture  is  reduced 
it  will  be  noticeable  by  the  decrease  in  the  amount 
of  light.  By  removing  the  eyepiece  and  looking  at  the 
back  of  the  objective  the  relative  aperture  of  the  con- 
denser to  that  of  the  objective  may  be  easily  seen,  as 
the  outlines  of  the  diaphragm  are  sharply  defined.  In 
testing  for  this  start  with  the  smallest  aperture  of  the 
diaphragm  and  gradually  increase  its  diameter.  If  the 
opening  in  the  diaphragm  appears  to  have  the  same  open- 
ing as  the  back  of  the  objective,  the  condenser  has  the 
same  angular  aperture.  In  the  following  instructions 
for  the  proper  use  of  light  from  the  condenser  the  size 
of  opening  of  its  diaphragm  as  it  appears  by  viewing 
the  back  of  the  objective  is  called  apparent  aperture. 
By  experience  the  following  conditions  have  been  found 
to  give  most  satisfactory  results : 

In  oil  immersion  objectives  on  bacteria  use  the  full 
opening  of  diaphragm. 

On  diatoms  reduce  the  apparent  aperture  to  about 
two-thirds  opening  in  objective. 

In  histological  and  other  dense  objects  use  the 
apparent  aperture  equal  to  about  one-half  the  opening 
of  back  lens  in  objective. 

In  dry  objectives  the  aperture  of  the  condenser  should 
always  be  less  than  that  of  the  objective. 

26 


Oblique  Light  with  Condenser.  Oblique 
light  may  be  obtained  by  setting  the  mirror  alone  in 
such  a  position  that  the  light  reflected  from  it  shall 
enter  the  condenser  only  at  one  side,  leaving  the 
balance  of  it  unused.  This,  however,  is  only  advisable 
when  the  condenser  mounting  has  no  other  provision 
for  obtaining  oblique  light.  In  the  mountings  having 
such  provision  oblique  illumination  may  be  obtained 
by  two  methods': 

/.  Focus  objective  ;  re- 
duce the  apparent  aperture 
to  that  of  the  rear  lens 
of  the  objective,  swing  the 
plate  o,  page  23,  carrying 
the  lateral  adjustment 
around  so  that  the  pinion 
button  is  at  the  front. 
Turn  the  pinion  button 
so  that  the  opening  will 
move  from  the  center  to  the  periphery  of  the  condenser. 

II.  Proceed  as  above  with  this  difference.  Remove 
eyepiece  and  view  the  bright  circle  of  light  as  it  passes 
from  the  center  to  the  periphery  of  the  rear  lens. 

When  the  circle  of  light  has  passed  beyond  the  limit 
of  aperture  of  the  objective  the  field  will  become  dark. 

In  objects  with  striated  structure,  the  illuminating 
rays  should  be  brought  to  a  position  at  right  angles  to 


Illuminating  object  by  oblique  light 
with  condenser. 


the  striae,  either  by  rotating  the  object  to   the  proper 
position,  or  by  swinging  the  diaphragm  plate. 

In  using  process  II  the  circle  of  light  should  be 
bright.  As  it  nears  the  edge,  colors  become  apparent 
until  finally  at  the  edge  of  the  objective  the  violet  and 
red  are  quite  pronounced.  With  proper  disposition  of 
the  mirror  the  colors  may  be  so  equalized  that  after  a 
little  practice  the  illumination  will  be  found  at  its  best 
after  the  eyepiece  is  applied. 

With  either  method  lamplight  will  be  found  to  give 
best  results,  but  care  must  be  taken  that,  as  the  dia- 
phragm passes  toward  the  oblique  point,  the  mirror  is 
also  adjusted  so  that  the  illumination  will  not  be  lost. 

In  the  Abbe  condenser  the  chromatic  aberration  is 
quite  apparent  with  extreme  oblique  illumination.  The 
field  ceases  to  be  equally  illuminated  and  all  the  colors 
of  the  spectrum  from  the  violet  to  the  red  are  plainly 
evident  within  the  field  of  view.  Under  these  condi- 
tions it  is  of  course  impossible  to  view  large  specimens 
without  slightly  shifting  the  mirror  so  as  to  move  the 
lightest  portions  of  the  spectrum  to  different  parts  of 
the  field.  With  small  specimens  the  mirror  should  be 
so  directed  that  the  light  or  yellow  portion  of  the 
spectrum  is  in  the  middle  of  the  field. 


CARE  OF  A  MICROSCOPE. 


Besides  acquiring  the  ability  to  properly  use  an 
instrument  with  its  accessories,  it  is  important  to  know 
how  to  keep  it  in  the  best  working  condition.  It  may 
be  said  without  reserve  that  an  instrument  properly 
made  at  the  outset  and  judiciously  used  should  hardly 
show  any  signs  of  wear  either  in  appearance  or  in  its 
working  parts,  even  after  the  most  protracted  use  ;  and 
further  than  this,  every  good  instrument  should  have  a 
provision  for  taking  up  lost  motion,  if  there  is  a  likeli- 
hood that  this  may  occur  in  any  of  the  parts. 

Especial  care  should  be  given  to  the  optical  parts, 
in  fact  such  care  that  they  will  remain  in  as  good  con- 
dition as  when  first  received,  after  any  amount  of  use. 
Accidental  injury  may  occur,  but  is  quite  unlikely  if  a 
systematic  manner  of  working  is  followed,  if  a  special 
receptacle  for  each  part  is  provided. 

Do  not  allow  any  person  except  your  teacher  to 
manipulate  your  microscope  or  accessories.  One 
person  may  be  expert  in  the  manipulation  of  one 
instrument  and  still  find  it  difficult  to  work  with 
another.  The  fine  adjustment  particularly  causes  the 

29 


greatest  difficulty,  as  in  some  instruments  the  move- 
ment of  the  fine  adjustment  is  in  a  direction  opposite 
to  that  of  the  micrometer  screw,  and  thus  the  objective 
as  well  as  the  object  is  endangered. 

If  the  microscope  is  to  be  carried  any  distance  it 
should  be  done  in  its  case. 

Avoid  exposure  of  the  microscope  to  direct  sunlight 
and  extreme  or  sudden  changes  in  temperature.  If  by 
chance  the  microscope  should  have  become  very  cold, 
as  during  transportation  in  winter,  allow  it  to  warm 
gradually. 

Care  of  the  Stand.  Keep  free  from  dust  is  one 
of  the  first  rules  to  be  observed.  When  not  in  use  place 
the  microscope  in  its  case  or  cover  with  a  bell  jar  or 
close  mesh  cloth  such  as  cotton  flannel  or  velvet  which 
should  reach  to  the  table.  If  the  case  will  not  receive 
the  entire  outfit,  remove  the  double  or  triple  nose-piece, 
it  these  form  part  of  it,  and  place  objectives  in  their 
cases  If  dust  settles  on  any  part  of  the  instrument 
remove  it  first  with  a  camel's  hair  brush  and  then  wipe 
carefully  with  a  chamois  skin,  wiping  with  the  grain  of 
the  finish  of  the  metal  and  not  across  it,  as  in  the  latter 
case  it  is  likely  to  cause  scratches. 

When  handling  the  stand,  grasp  it  by  the  pillar  or 
stage.  While  the  arm  is  the  most  convenient  part  it  is 
at  the  same  time  the  most  dangerous  to  the  fine 
adjustment. 

3°  • 


Avoid  sudden  jars,  such  as  placing  upon  the  table 
or  into  the  case  with  force. 

Remove  any  Canada  balsam  or  cedar  oil  which  may 
adhere  to  any  part  of  the  stand  with  a  cloth  moistened 
with  benzole  and  wipe  dry  with  chamois. 

Use  no  alcohol  on  any  part  of  the  instrument  as  it 
will  remove  the  lacquer.  As  the  latter  is  for  the 
purpose  of  preventing  oxydization  of  the  metals,  it  is 
important  to  observe  this  rule. 

To  use  the  draw-tube  impart  the  spiral  motion. 

To  lubricate  any  of  the  parts,  use  a  slight  quantity 
of  soft  tallow  or  good  clock  oil,  or  paraffine  oil. 

If  the  pinion  works  loose  from  the  jar  incident  to 
transportation  or  long  use,  which  sometimes  occurs  to 
such  an  extent  that  the  body  will  not  remain  in  position, 
increase  its  tension  by  tightening  the  screws  on  pinion 
cover. 

Occasionally  withdraw  the  tube  from  the  arm,  wipe 
clean  and  lubricate  both  slides.  This  is  highly  important 
as  the  slides  being  constantly  exposed  become  dusty 
and  the  lubricant  is  inclined  to  gum. 

Apply  a  small  quantity  of  soft  tallow  or  good  clock 
or  paraffine  oil  to  a  cloth,  wipe  well  over  the  surfaces 
and  remove  the  superfluous  amount  with  a  dry  cloth  or 
Japanese  paper.  If  the  lubricant  becomes  gummy, 
remove  by  wiping  with  a  small  quantity  of  benzine  or 
benzole  applied  to  cambric. 


Do  not  apply  oil  or  grease  to  the  rack  or  pinion 
as  this  will  act  as  a  dirt  catcher  and  wear  out  the  teeth 
at  the  points  of  contact. 

In  inclining  the  stand  always  grasp  it  by  the  arm 
and  never  by  the  tube,  as  in  the  latter  case  it  may 
loosen  the  slide  or  tear  off  some  of  the  parts. 

In  using  a  screw  driver  grind  its  two  large  surfaces 
so  that  they  are. parallel  and  not  wedge-shaped,  so  it 
will  exactly  fit  in  the  slot  of  the  screw-head.  Turn  the 
screw  with  a  slow  steady  motion  pressing  the  screw- 
driver firmly  into  the  slot.  No  screw-head  will  ever 
be  injured  if  these  points  are  observed. 

When  repairs  or  alterations  are  necessary,  always 
have  these  made  by  the  manufacturers  who  can,  from 
a  system  of  duplicated  parts,  do  it  not  only  cheapest, 
but  best. 

Joint  for  Inclination.  If  the  joint  should 
become  loose  so  as  to  prevent  the  arm  being  set  at 
any  angle  of  inclination,  it  should  be  tightened  by 
drawing  up  the  nut  at  one  or  the  other  side.  If  the 
nut  has  screw  slot  use  a  properly  prepared  screw 
driver,  but  if  two  holes  a  suitable  key  should  be 
obtained  from  the  maker.  In  high  grade  instruments 
the  axle  is  generally  tapering,  and  to  determine  which 
nut  is  to  be  drawn  up  can  only  be  done  by  trial. 


Care  of  the  Coarse  Adjustment.  Special 
care  should  be  given  to  keep  the  coarse  adjustment 
free  from  dust  as  its  effect  is  particularly  pernicious. 
The  slides  and  rack  and  pinion  are  necessarily  exposed 
and  the  lubricant  is  apt  to  catch  dust  and  also  to  gum. 
The  tube  should  be  occasionally  withdrawn  from  the 
arm  and  the  slides  carefully  wiped  with  a  cloth 
moistened  with  benzole.  Lubricate  by  applying  a 
small  quantity  of  soft  tallow  or  paraffine  oil  to  a  cloth 
and  wiping  well  over  the  surfaces,  removing  the  super- 
fluous amount  with  a  dry  cloth.  The  teeth  of  neither 
rack  nor  pinion  should  ever  be  lubricated.  An 
occasional  cleaning  of  the  teeth  with  an  old  tooth 
brush  is  advisable. 

It  is  advisable  occasionally  to  lubricate  the  pinion 
shank  on  both  sides  of  the  arm  with  a  very  minute 
quantity  of  paraffine  oil. 

If  the  pinion  works  loose  from  jar  incident  to  trans- 
portation or  long  use,  which  sometimes  occurs  to  such 
an  extent  that  the  body  will  not  remain  in  position, 
increase  the  friction  upon  it  by  tightening  the  screws 
on  the  pinion  cover. 

Fine  Adjustment.  In  a  general  way  it  may  be 
said  that  if  the  fine  adjustment  ceases  to  work  satis- 
factorily the  instrument  had  better  be  returned  to  the 
maker,  as  it  involves  the  most  delicate  working  and 
few  people  are  conversant  with  its  construction.  There 

33 


is  very  seldom  any  occasion  for  this,  however,  if  used 
with  reasonable  care. 

If  the  fine  adjustment  does  not  respond  to  the 
turning  of  the  micrometer  screw,  or  if  it  comes  to  a 
stop,  it  indicates  that  the  adjustment  screw  has  come 
to  the  limit  of  its  motion  at  either  end.  It  should  by 
no  means  be  forced ;  it  should  at  all  times  be  kept  at 
a  medium  point. 

The  micrometer  screw  should  never  be  removed 
unless  after  long  use  it  works  with  a  pronounced  gritty 
feeling.  In  this  case  unscrew  from  its  bearing,  wipe 
clean  with  a  cloth  moistened  with  benzole,  and  after 
wiping  dry  apply  good  tallow,  being  careful  to  start  the 
threads  properly.  If  they  are  not  properly  started 
much  mischief  may  be  done.  In  some  instruments  the 
threads  are  left  handed.  In  removing  the  screw 
observe  whether  there  is  a  small  steel  pin  in  a  recess 
in  it,  and  if  so  be  careful  that  this  is  in  proper  position 
when  returned  or  else  the  fine  adjustment  will  be 
inoperative. 

Screw-Driver.  Ordinary  screw-drivers  are  not  fit 
for  use  on  the  microscope.  A  properly  made  screw- 
driver should  be  ground  on  its  two  large  surfaces  so 
that  they  are  parallel  and  not  wedge  shaped,  so  that  it 
will  exactly  fit  in  the  slot  of  the  screw  head.  In  using, 
turn  the  screw  with  a  slow,  steady  motion,  pressing  the 
screw-driver  slowly  into  the  slot.  No  screw  head  will 
ever  be  injured  or  marred  if  these  points  are  observed. 

34 


Care  of  Objectives  and  Eyepieces.  Every 
outfit  should  be  provided  with  a  camel's  hair  brush 
and  a  well  washed  piece  of  linen.  On  account  of  its 
fine  texture  chamois  skin  is  desirable,  but  only  after  it 
has  been  repeatedly  washed.  No  dust  should  be  per- 
mitted to  settle  upon  nor  should  the  fingers  come  in 
contact  with  any  of  the  surfaces.  Occasional  cleaning 
is  desirable  even  when  they  ( ' o  and  e  p )  are  not  used, 
as  a  film  settles  upon  the  outer  as  well  as  the  inner 
surfaces  of  the  eyepiece  and  the  rear  surface  of  the 
objective,  and  creates  a  cloudiness  in  the  image. 

When  not  in  use  objectives  and  eyepieces  should 
be  kept  in  their  receptacles.  If  objectives  are  left 
attached  to  the  microscope  either  singly  or  on  revolv- 
ing nose-pieces,  leave  the  eyepiece  in  the  tube  so  that 
no  dust  can  enter  and  settle  upon  the  rear  lens  of 
the  objective. 

Objectives  especially  should  be  kept  where  they 
are  not  subject  to  extreme  and  sudden  changes  of 
temperature  as  the  expansion  and  contraction  may 
cause  the  cement  between  the  lenses  to  crack.  Also 
avoid  direct  sunlight,  as  the  cement  may  soften 
sufficiently  to  ooze  out. 

Eyepiece.  Visible  defects  in  the  field  are  always 
traceable  to  impurities  in  the  eyepiece,  not  in  the 
objective,  and  are  easily  recognized  by  revolving  it. 
Indistinctness  in  the  image  or  loss  of  light  may  be  due 

35 


to  soiled  or  coated  surfaces  in  either  eyepiece  or 
objective. 

Dust  if  on  either  the  eye-lens  or  field-lens  is  apparent 
as  dark,  indistinct  spots. 

To  clean  the  surfaces,  breath  upon  them  and, 
giving  a  revolving  motion  to  the  eyepiece,  wipe  with 
well  washed  linen  and  finally  blow  upon  the  surface,  or 
use  camel's  hair  brush  to  remove  particles  of  lint. 

At  regular  periods  unscrew  the  eye-lens  and  field 
lens  and  clean  the  inner  surfaces. 

Objective.  This  should  be  used  with  the  utmost 
care.  The  systems  should  never  be  separated,  even  if 
they  can  be  unscrewed,  as  they  are  liable  to  become 
decentered  and  dust  may  enter. 

Avoid  all  violent  contact  of  the  front  lens  with  the 
cover  glass.  The  oil  immersion  objectives  are  partic- 
ularly sensitive  and  easily  ruined. 

Screw  into  the  nose-piece  and  unscrew  by  grasping 
the  knurled  edge  and  keeping  in  line  with  the  tube. 

Occasionally  examine  the  rear  surface  of  the  objec- 
tive with  magnifier  and  if  dust  be  present  remove  with 
camel's  hair  brush. 

Clean  an  immersion  objective  immediately  after  it 
has  been  used  by  removing  the  fluid  with  moist  cloth 
and  wiping  clean  with  dry  cloth  or  lens  paper. 

While  cleaning  give  the  objective  a  revolving  motion. 

36 


If  the  immersion  oil  should  hare  become  thick,  or 
any  substance  adheres  to  the  surface,  which  cannot  be 
removed  by  wiping,  apply  a  small  amount  of  benzine 
to  a  cloth  and  wipe  carefully  but  quickly,  so  that  the 
fluid  will  not  affect  the  setting  of  the  lens.  Wipe  clean 
with  dry  cloth. 

Do  not  apply  alcohol  to  objectives  under  any  con- 
dition. 


If  any  part  of  the  microscope  cannot  be  brought  to 
a  satisfactory  working  condition  by  the  foregoing 
instructions,  or  any  part  is  injured  by  accident  it  should 
invariably  be  sent  to  the  maker  or  to  a  well  known 
manufacturer  of  microscopes. 


INDEX. 


Abbe  Condenser 
Aperture  of  Condenser  25 
Apparent  Aperture         26 

Care  of  Microscope  29,  37 

Cedar  Oil  14,  31 

Centering  Condenser    22 

Centeringlllumination  23 

Coarse  Adjustment        33 

Complete  Substage        23 

Concave  Mirror          8,  22 

Condenser  21 

Aperture  of  25 

Oblique  Light  with    27 

To  Center  22 

To  Focus  24 

Cover  Glass  17 


Diaphragm 

How  to  Use 
Draw  Tube 


16 

26 

1,  3 


Eye,  Which  to  Use  16 

Eyepiece,  To  Attach  3 

Care  of  35 

Eyepoint  17 

Finding  an  Object  6 

Fine  Adjustment  15,  33 
Focusing  Condenser  24 
Focusing  Objectives  11,15 

Immersion  Objectives  14 
Immersion  Oil  14,  37 
Illuminating  Object  7,  21 
Illumination, To  Center  23 

Joint  for  Inclination      32 


Micrometer  Screw          34 

Microscope,  Care  of  29, 37 

Correct  Position  at       2 

To  Set  Up  1 

Mirrors  7,  8 

Nose-Piece,  To  Attach    5 
To  Focus  with  14 

Object,  To  Find         6,  12 
To  Illuminate    7,  22,  27 

Objective,  To  Attach     4,5 

Aperture  of  26 

Care  of  35,  36 

Cover  Glass  with         18 

Oil  Immersion  14 

To  Focus  11 

To  Test  19 

Oblique  Light  27 

OilImmersionObjectivel4 

Over-Correction  19 

Par  Focal  Objectives  13 
Pinion  31 

Plane  Mirror  7,  22 

Screw  Driver  32,  34 

Searcher  Objective         13 
Spherical  Correction     17 
To  Test  for  19 

Stand,  Care  of  30 

Substage,  Complete  23 
Substage  Condenser  21 
Substage  Diaphragm  16 
Tube  Length  1,  13,  19,  20 
Under-Correction  19 


MANUFACTURES 

of  the 

BAUSCH    &    LOMB    OPTICAL   CO. 
MICROSCOPES 

Objectives,  Micrometers,  Camera  Lucidas,   Magnifiers, 

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and  Imbedding  Substances,  etc. 

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Fine  Dissecting  Instruments,  etc. 

PHOTOGRAPHIC  APPARATUS 

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Shutters,  Complete  Photomicrographic  Cameras, 

Projection  Apparatus,  etc. 

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BACTERIOLOGICAL  APPARATUS 

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CHEMICAL  APPARATUS  &  CHEMICALS 

Fine  Balances,  Pure  Platinum  Ware,  Glassware  of 
every  description,  Analytical  Chemicals,  etc. 


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